Archive for the ‘Debian’ Category

I’ve posted a recipe for chrooting MySQL on Debian sarge a while ago. These instructions no longer work out of the box for newer MySQL packages from Debian and Ubuntu. The main problem is that the startup script added a few extra checks and script invocations that don’t understand the chroot environment. So here’s an updated plan:

Prepare the chroot directory. It’s recommended to use an extra partition/filesystem for it. I will use /srv/mysql (which is an LVM2 partition with an ext3 filesystem on my system) for the rest of the text.

Sun now allows redistribution of Java by Linux and Open-Solaris distributions.

As a result of this move, there are now packages of Sun’s Java for Debian and Ubuntu.
The packaging code is largely based on the code we are using for Blackdown Java for some years. The code is available under the MIT license from the jdk-distros project on java.net. (More info on Tom Marble’s blog.)

I have upgraded this server to kernel 2.6.16.2. The next backup cycle resulted in a minor disaster: The backup process deadlocked at removing the first LVM2 snapshot and the snapshot source volumes were blocking write accesses. A cleanup shutdown was impossible and I had to hard-reset the machine.

After some searching I found out that you apparently need lvm2 2.02.01 or later and devmapper 1.02.02 or later to successfully remove snapshot volumes now. Unfortunately neither of these versions is available for sarge from Debian or backports.org yet, so I had to make my own backports.
As it turned out (see below), it is also necessary to use 2.6.16.12 or to apply the patch from this email to older 2.6.16 versions in order to reliably remove snapshots.

If you are brave enough, you can get the backported packages by adding

The repository contains debs for devmapper, dlm, lvm2, and lvm-common. The Release files is signed with my GPG key. If you have a recent apt version, you can authenticate the packages after importing the key with apt-key:

The situation has not changed much since WordPress 1.5: WordPress 2.0 still does not support HTTPS access to the admin area when the rest of the blog is served via normal HTTP and I still do not like logging in to my server over unencrypted connections, especially not when using public WLANs. Getting around this WordPress limitation requires quite a few steps:

The Goal

All communication involving passwords or authentication cookies should be done over HTTPS connections. wp-login.php and the wp-admin directory should only be accessible over HTTPS.
Normal reading access, as well as comments, tracebacks, and pingbacks still should go over ordinary HTTP.

The Plan

Add an HTTPS virtual host that forwards requests to the HTTP virtual host

Modify WordPress to send secure authentication cookies, so cookies never get sent over insecure connections accidentally

Require a valid certificate on HTTPS clients. That means to log in to WordPress you need both a valid certificate and a valid password. If someone manages to get your password, he still can not login because he does not have a valid certificate.

The Implementation

Note: This documentation assumes a Debian sarge installation with Apache 2. Some things, in particular Apache module related ones, will be different on other systems.
The server used throughout the instructions is example.org/192.0.34.166. The server’s DocumentRoot is /blog and WordPress resides in /blog/wp. The value of WordPress’ home option is ‘http://example.org’ and the value of its site_url option is ‘http://example.org/wp’.

Prepare the SSL certificates:

Generate your own certificate authority (CA) if you don’t have one already (I’m using the makefile from OpenSSL Certificate Authority Setup for managing mine) and import it into your browser.

Generate a certificate for the SSL server and certify it with your private CA.

Generate a certificate for your browser and certify it with your private CA. Most browsers expect a PKCS#12 file, so generate one with

Make WordPress SSL-ready:
Apply this patch to the WordPress code. It makes the following changes:

Use secure authentication cookies in wp_setcookie()

Make check_admin_referer() work with HTTPS URLs

Use HTTPS URLs for notification mails

Use HTTPS URLS for redirects to wp-login.php

Only allow XML-RPC logins from the local host (ie. the HTTPS proxy)

Add the Mark-as-Spam feature from trunk

The patch is against svn version 3825 of WordPress (ie. WordPress 2.0.3), when you apply it to a newer version, you will likely get some harmless ‘Hunk succeeded’ message. If you are getting ‘Hunk FAILED’ message, just send me note and I’ll update the patch.

Enable the necessary Apache modules:

Install mod_proxy_html. It will be used to replace absolute ‘http://example.org’ HTTP URLs in the WordPress output with ‘https://example.org’ HTTPS URLs:

$ aptitude install libapache2-mod-proxy-html

The module gets enabled automatically after installation.

Enable mod_proxy and mod_ssl

$ a2enmod proxy
$ a2enmod ssl

Debian provides sane default configurations for both modules. You might want to take a look at the configuration files (ssl.conf and proxy.conf) nevertheless.
I have changed SSLCipherSuite to

Modify the blog virtual host to limit access to wp-login.php and wp-admin to the local host. Also completely deny access to files which should never be accessed directly. Here is an example: 10-wp2-example.org

Now setup the HTTPS virtual server: 20-wp2-example.org-ssl
If you are compressing WordPress output you have to enable the RequestHeader line.